How can I have Alpha 0 but only shows highlight
Using Eevee, you can use the &quot;shader to RGB&quot; node from a &quot;glass&quot; node. &quot;shader to RGB&quot; is like a prerendering from with we can get colors.

From it, we can use 2 color ramps: the first to control the light reflexion intensity and color and the other to control the level of transparency.

Color is given directly to the Principled and its alpha value is given by the intensity of the light.
Make sure to set the object transparent (alpha blend) in Eevee material settings.

Alternatively, you can also keep the original environment/light colors with this setting (look nicer, I think, but...):